Motion platforms, otherwise known as motion simulators, are used to simulate the sensation of being in a moving vehicle, for example an aircraft or motor car. Motion simulators typically comprise some form of enclosure, capsule or cockpit having one or more seats for occupants and a sound and visual display which is synchronised to the movement of the enclosure. The enclosure can be moved within a given working volume through an arbitrary trajectory in a 3 dimensional space. To facilitate such movement the enclosure is usually mounted on some form of supporting surface or platform having series of underlying actuators to impart motion, for example a Stewart platform.
Stewart platforms are well-known and permit movement with 6 degrees of freedom, i.e. independent and simultaneous translation and rotation about and along each of the three primary Cartesian axes X, Y and Z. A Stewart platform includes six legs each of which is extendible to translate and rotate a supporting platform about all three Cartesian axes. A typical Stewart platform, as shown in FIG. 1 of the accompanying drawings, includes a base structure 3 which is spaced from a support platform 5 by a plurality of extendible legs in the form of hydraulic, pneumatic, or electric actuators 7.
In existing motion simulators the entire weight of the enclosure, including the occupants, is supported solely by the actuators 7. The actuators 7 must therefore be adequately sized to support weight of the enclosure and impart the required motion.